Recovery of hydrogen from refinery and petrochemical light ends streams

Abstract

A process for recovering hydrogen from a stream comprised of hydrogen, non-condensable gases, and propane and lighter hydrocarbons, wherein the process comprises the steps of stripping hydrogen and non condensable gases out of the feed light ends stream with methane vapor, washing the stripped hydrogen stream with liquid methane to absorb the non condensable gases, and washing the hydrogen stream with a hydrocarbon lean oil such as liquid ethane to absorb methane, to produce the product hydrogen stream.

Description

FIELD OF THE INVENTION [0001] This invention relates to recovering hydrogen from light ends streams produced in petroleum refineries and petrochemical plants. BACKGROUND OF THE INVENTION [0002] Hydrogen is used in petroleum refineries to remove sulfur from fuel products and to saturate olefins and aromatics to make chemical products. Hydrogen is produced as a byproduct in petroleum refineries and petrochemical plants. Byproduct hydrogen collects in light ends streams containing light hydrocarbons and also non-condensable gases-including carbon monoxide, carbon dioxide, and nitrogen. The light ends streams are usually processed to recover propane, propylene and heavier hydrocarbons using conventional fractionation techniques at ambient temperatures, and then further processed to recover ethylene, ethane and hydrogen at cryogenic temperatures. Streams processed at low temperatures are usually dried to remove water and treated to remove corrosive compounds including hydrogen cyanide, h...

AI Technical Summary

Benefits of technology

"The present invention is a process for recovering high yield and purity hydrogen from refinery and petrochemical light ends streams. The process involves stripping the most of hydrogen and non-condensable gases out of the feed stream, absorbing them out of the hydrogen stream using a liquid methane stream, and absorbing methane out of the hydrogen stream using a lean oil stream. The process includes a series of strippers, rectifier tower, reboiled absorber, and methane absorber. The invention allows for the efficient recovery of hydrogen from a variety of feed streams without the need for additional facilities or the production of pure methane."

Problems solved by technology

In most refining and petrochemical sites recovered byproduct hydrogen is not adequate to meet demand.

Unfortunately, on purpose hydrogen costs about three times as much as recovered byproduct hydrogen and also releases carbon dioxide into the environment.

A primary reason why hydrogen recovery rates are low with current technology is that hydrogen bearing light ends streams usually contain non-condensable gases—nitrogen and carbon monoxide—and these gases are difficult to separate from hydrogen with current technology.

Images